OS BIG Editor 0.5 is a .BIG an open source file browser compatible with Generals and newer Command & Conquer games. It allows you to browse the .big files, preview the .tga and text files and extract the files inside them.

This tool has a webpage at:
http://www.ppmsite.com/index.php?go=osbigeditorinfo

Support for OS BIG Editor is available at:
http://www.ppmforums.com/index.php?f=102